1. Field of the Invention
The invention relates to hydrogen sensors, and, particularly, to nanoscale antiferromagnetic hematite sensors.
2. Related Art
Hydrogen sensing is a critical component of safety necessary to address widespread public perceptions of the hazards of production, storage, transportation and use of hydrogen in proposed future automobiles and in various other applications. The need to detect leaks from hydrogen-powered cars long before the gas becomes an explosive hazard (<4% H2 in air) makes it necessary to develop such sensors to be small enough to be incorporated into the vehicles' engines as well as suitable for operation in highly mobile environments. Commercial solid-state gas sensors employing the electrical properties of oxide semiconductors suffer from low sensitivity, serious difficulties associated with complex electrical contacts especially when used in mobile environments, and degradation of the material surface and electrical contacts when used in reactive chemical environments.
Since oxygen vacancies are primarily produced on the surface of the particles/films, the inventor proposes that a way to significantly improve gas sensitivity is to develop new methods that utilize the high surface area of particles produced in the nanoscale form. However, nanoscale powders with very large surface-to-volume ratios cannot be used in the conventional electrical-property-based sensing methods because stable electrical contacts are extremely difficult to make on powders and nanoparticles. Therefore, there is still a need for an effective nanoscale hydrogen gas sensor that overcomes these problems.
The present invention meets the need for a nanoscale hydrogen sensor. Preferred embodiments exhibit varying saturation magnetization and remanence of nanoscale antiferromagnetic hematite with increasing concentration of hydrogen gas, and, thus, facilitate the magnetic properties to be used as novel gas sensing parameters. A magnetic hydrogen sensor employing changes in the magnetic force experienced by a magnetized metal nonorod as a result of changes in the sample magnetization of a nanoscale hematite powder is described.